import java.util.ArrayList;
import java.util.LinkedList;

/*
 * @lc app=leetcode.cn id=316 lang=java
 *
 * [316] 去除重复字母
 */

// @lc code=start
class Solution {
    public String removeDuplicateLetters(String s) {
        Queue<String> q1 = new LinkedList<>();
        String str = "";
        char[] chs =  s.toCharArray();
        ArrayList<Character>  list = new ArrayList<>();
        
        return str;
    }
}
// @lc code=end

